I used tinyFAT for the following first test with a Sandisk 2GB FAT16 micro SD card - it worked perfectly - I will test others later - more to come!

// Demo_writeLn (C)2011 Henning Karlsen
// web: http://www.henningkarlsen.com/electronics
//
// modified by fgm for speaking vario test - first try
//
// This program is a demo of the writeLn()-function.
//
// This demo will create a textfile, and fill it with 1MB
// of text. The file will be named 'BIGFILE.TXT'. If the
// file already exists it will first be deleted.
//
// SD card must be connected to the SPI port of your Arduino.
//
// Remember to select 115200 baud in the Serial Monitor.
//

Serial.println("This demo will create a textfile, and fill it with 1MB of text.");
Serial.println("The file will be named 'BIGFILE.TXT'. If the file already exists it will first be deleted.");
Serial.println();
Serial.println("***** Send any character to start *****");
while (!Serial.available()) {};
Serial.flush();
//=====================================================================================================================
char filenamebuffer[50];
sprintf(filenamebuffer, "FILEDATA.TXT");
Serial.println(filenamebuffer);